"People are going to be shocked, because nobody knows," said Zolciak, who posed for a Life & Style photo shoot to be featured in this week's issue.
While the reality TV star -- who welcomed a son, Kroy Jagger, into the world with Biermann in June 2011 -- revealed she doesn't know the sex of the baby yet, she will seemingly be thrilled with either a boy or a girl.
"I'm so excited that KJ will have a little buddy," Zolciak explained.
Zolciak got engaged to Biermann in October 2011 and then quickly married the Atlanta Falcons football player one month later.
The new baby will be the reality TV star's fourth child. While KJ is the first baby for Zolciak and Biermann, he is Zolciak's third child and joined her two daughters 14-year-old Brielle and nine-year-old Ariana from a previous relationship.
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